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SDLT 600 SCSI Interface Guide Chapter 4: SCSI Commands

81-81200-02 REV A01 January 2005 4-147

05h Pre-empt

& Clear

A PERSISTENT RESERVE OUT command with a Pre-empt & Clear

service action removes all persistent reservations for all initiators that

have been registered with the service action Reservation Key specified in

the PERSISTENT RESERVE OUT command’s parameter list. It also

establishes a persistent reservation for the pre-empting initiator. Any

commands from the initiators being pre-empted are terminated as if the

pre-empted initiator had performed an ABORT TASK management

function. If a PERSISTENT RESERVE OUT command is sent that

specifies a Pre-empt & Clear service action and no persistent reservation

exists for the initiator identified by the service action Reservation Key, it

is not an error condition. If the key is registered, however, the Clear

portion of the action executes normally.

A UNIT ATTENTION condition is established for the pre-empted

initiators. The Sense Key is set to UNIT ATTENTION, the Additional

Sense Code is set to RESERVATIONS PREEMPTED. Commands that

follow, and retries of commands that timed out because they were

cleared, are subject to the persistent reservation restrictions set by the

pre-empting initiator.

The persistent reservation the pre-empting initiator created is defined by

the Scope and Type fields of the PERSISTENT RESERVE OUT

command and the corresponding fields of the command’s parameter list.

The Pre-empt & Clear service action clears any CA condition with the

initiator that is pre-empted.

The Reservation Keys for the other initiators pre-empted are removed by

the Pre-empt & Clear service action. The Reservation Key for an initiator

that has sent a Pre-empt & Clear action with its own Reservation Key

specified in the service action’s Reservation Key remains unchanged,

although all other specified clearing actions, releasing actions, and

reservation actions are performed.

Persistent reservations are not superseded by a new persistent reservation

from any initiator except by executing a PERSISTENT RESERVE OUT

command that specifies either the Pre-empt or Pre-empt & Clear service

action. New persistent reservations not in conflict with an existing

persistent reservation execute normally.

06h Register

and

Ignore

Key

Behaves like the Register (00h) action except that it ignores the

Reservation Key in the parameter list and treats it as if it matched the

current registration, if one exists, for the initiator.

Table 4-83. PERSISTENT RESERVE OUT Command’s Service Action Descriptions (Continued)

Code Name Description

1 2 ... 184 185 186 187 188 189 190 191 192 193 194 ... 293 294

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